Preheat the oven to 400ºF (~205ºC). Line a large baking sheet with a silicone mat or parchment paper.
Chop the cauliflower into small florets. I like to chop the florets in half or into quarters, depending on the size of each floret.
In a large bowl, mix the florets, 1 and 1/2 tablespoons of olive oil, 1/2 tablespoon of za'atar, and 1 teaspoon of sea salt together. Place the florets on the baking sheet and bake for about 25 minutes, or until they are slightly browned.
Pour 3 cups of cooked millet into the same bowl that you used to toss the cauliflower. Feel free to substitute the millet with your favorite grains.
Mix the millet with the rest of the oil, za'atar, salt, and feta.
Serve the millet with the roasted cauliflower and enjoy it as a side dish. Refrigerate any leftovers in an airtight container.